GHSA-2G4M-3WVW-CRQ2

Vulnerability from github – Published: 2026-04-01 09:31 – Updated: 2026-06-30 03:36
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

KVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE

When installing an emulated MMIO SPTE, do so after dropping/zapping the existing SPTE (if it's shadow-present). While commit a54aa15c6bda3 was right about it being impossible to convert a shadow-present SPTE to an MMIO SPTE due to a guest write, it failed to account for writes to guest memory that are outside the scope of KVM.

E.g. if host userspace modifies a shadowed gPTE to switch from a memslot to emulted MMIO and then the guest hits a relevant page fault, KVM will install the MMIO SPTE without first zapping the shadow-present SPTE.

------------[ cut here ]------------ is_shadow_present_pte(*sptep) WARNING: arch/x86/kvm/mmu/mmu.c:484 at mark_mmio_spte+0xb2/0xc0 [kvm], CPU#0: vmx_ept_stale_r/4292 Modules linked in: kvm_intel kvm irqbypass CPU: 0 UID: 1000 PID: 4292 Comm: vmx_ept_stale_r Not tainted 7.0.0-rc2-eafebd2d2ab0-sink-vm #319 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:mark_mmio_spte+0xb2/0xc0 [kvm] Call Trace: mmu_set_spte+0x237/0x440 [kvm] ept_page_fault+0x535/0x7f0 [kvm] kvm_mmu_do_page_fault+0xee/0x1f0 [kvm] kvm_mmu_page_fault+0x8d/0x620 [kvm] vmx_handle_exit+0x18c/0x5a0 [kvm_intel] kvm_arch_vcpu_ioctl_run+0xc55/0x1c20 [kvm] kvm_vcpu_ioctl+0x2d5/0x980 [kvm] __x64_sys_ioctl+0x8a/0xd0 do_syscall_64+0xb5/0x730 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x47fa3f ---[ end trace 0000000000000000 ]---

Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-23401"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-04-01T09:16:15Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE\n\nWhen installing an emulated MMIO SPTE, do so *after* dropping/zapping the\nexisting SPTE (if it\u0027s shadow-present).  While commit a54aa15c6bda3 was\nright about it being impossible to convert a shadow-present SPTE to an\nMMIO SPTE due to a _guest_ write, it failed to account for writes to guest\nmemory that are outside the scope of KVM.\n\nE.g. if host userspace modifies a shadowed gPTE to switch from a memslot\nto emulted MMIO and then the guest hits a relevant page fault, KVM will\ninstall the MMIO SPTE without first zapping the shadow-present SPTE.\n\n  ------------[ cut here ]------------\n  is_shadow_present_pte(*sptep)\n  WARNING: arch/x86/kvm/mmu/mmu.c:484 at mark_mmio_spte+0xb2/0xc0 [kvm], CPU#0: vmx_ept_stale_r/4292\n  Modules linked in: kvm_intel kvm irqbypass\n  CPU: 0 UID: 1000 PID: 4292 Comm: vmx_ept_stale_r Not tainted 7.0.0-rc2-eafebd2d2ab0-sink-vm #319 PREEMPT\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n  RIP: 0010:mark_mmio_spte+0xb2/0xc0 [kvm]\n  Call Trace:\n   \u003cTASK\u003e\n   mmu_set_spte+0x237/0x440 [kvm]\n   ept_page_fault+0x535/0x7f0 [kvm]\n   kvm_mmu_do_page_fault+0xee/0x1f0 [kvm]\n   kvm_mmu_page_fault+0x8d/0x620 [kvm]\n   vmx_handle_exit+0x18c/0x5a0 [kvm_intel]\n   kvm_arch_vcpu_ioctl_run+0xc55/0x1c20 [kvm]\n   kvm_vcpu_ioctl+0x2d5/0x980 [kvm]\n   __x64_sys_ioctl+0x8a/0xd0\n   do_syscall_64+0xb5/0x730\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n  RIP: 0033:0x47fa3f\n   \u003c/TASK\u003e\n  ---[ end trace 0000000000000000 ]---",
  "id": "GHSA-2g4m-3wvw-crq2",
  "modified": "2026-06-30T03:36:06Z",
  "published": "2026-04-01T09:31:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23401"
    },
    {
      "type": "WEB",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23401.json"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fd28c5618699180cd69619801e9ae6a5266c0a22"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ed5909992f344a7d3f4024261e9f751d9618a27d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bce7fe59d43531623f3e43779127bfb33804925d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/aad885e774966e97b675dfe928da164214a71605"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/695320de6eadb75aaed8be1787c4ce4c189e4c7b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/459158151a158a6703b49f3c9de0e536d8bd553f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/20656cd1f243d3a154aac5dd1b823110b6906fe1"
    },
    {
      "type": "WEB",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2453803"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/security/cve/CVE-2026-23401"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:20593"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:19875"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:19569"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:19568"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:19521"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:15883"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:14339"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:14230"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:14137"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:13936"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:13932"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:13578"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:13577"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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